Explanations:Conjunctions are words that connect clauses or sentences and show the relationship between them. There are several types of conjunctions, including coordinating conjunctions, subordinating conjunctions, and conjunctions of contrast. Conjunctions of contrast are used to connect two clauses that have opposing or contrasting ideas. Common conjunctions of contrast include "but," "however," and "although."
In the given sentence, "Betty is usually on time, _____ tonight she arrived late," the conjunction of contrast "but" is the correct choice. The sentence presents a contrast between Betty's usual punctuality and her tardiness on this particular night. The conjunction "but" is used to show that the second clause presents a situation that is different from or opposite to the first clause.
Let's examine why the other options are incorrect:
"So" is a coordinating conjunction that is used to show a result or consequence. For example, "Betty studied hard, so she passed the exam." In this sentence, "so" indicates that Betty's studying led to her passing the exam. However, in the given sentence, there is no indication that Betty's usual punctuality caused her to arrive late tonight.
"And" is a coordinating conjunction that is used to add information. For example, "Betty is usually on time, and she is very responsible." In this sentence, "and" is used to add information about Betty's character. However, in the given sentence, the second clause presents a contrasting idea, not additional information.
"Because" is a subordinating conjunction that is used to show a cause and effect relationship. For example, "Betty arrived late because she missed the bus." In this sentence, "because" indicates that Betty's tardiness was caused by missing the bus. However, in the given sentence, there is no indication that Betty's usual punctuality is the reason for her tardiness tonight.
"Then" is a time conjunction that is used to show a sequence of events. For example, "Betty finished her homework, then she went to bed." In this sentence, "then" indicates that Betty went to bed after finishing her homework. However, in the given sentence, there is no indication that Betty's tardiness is a result of her usual punctuality.
Therefore, the correct conjunction to use in the sentence "Betty is usually on time, _____ tonight she arrived late" is "but," as it effectively shows the contrast between Betty's usual punctuality and her tardiness tonight.